To remove varnish or lacquer from wood take some denatured alcohol and lacquer thinner and combine equal parts denatured alcohol and lacquer thinner or paint thinner together and brush it onto the wood and let it sit for around an hour to allow it to work.
Then use a paint scraper to scrape the varnish up and follow it up by sanding the wood down for a nice new finish.
Paint remover should also work to remove varnish from wood after you let it sit for an hour or so and then scrape it up as well and sand it down.